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Prediction models of non-ferrous secondary raw materials formation
No full textFor the prediction of formation of non-ferrous processing and accumulating waste both model of balancing and model of correlation and regression analysis can be employed, while the dynamic model can be applied only for the accumulating waste. Estimates of the formation of certain type of metallic secondary raw materials in model of balancing are based on data of production and consumption of metals and on the numerical values of the waste formation coefficients. Applying of correlation and regression analysis method on the assessment of metallic waste formation is based on finding the functional dependence between the creation of metallic waste and quantity of waste on the input stream of processing as well as correlation with metal fund for accumulation waste. The dynamic model are linking the effect of the products materials content and design on the amount of the quantity of the used products which are recycled over time, including various external influential factors
Flue gas desulphurisation in Serbia: Technologies, legal and economic aspects
No full textSagorevanjem uglja emituje se sumpor-dioksid (SO2), koji štetno utiče na životnu sredinu i zdravlje ljudi. Postrojenja za proizvodnju električne energije emituju najveći deo sumpor-dioksida u Srbiji. Propisi iz oblasti zaštite životne sredine u Srbiji nalažu postepenu implementaciju tehnologija za tretman dimnih gasova, odnosno kontrolu emisija zagađivača u atmosferu. Što se termoelektrana u Srbiji tiče, pripremljeni su idejni projekti za odsumporavanje dimnih gasova za dve termoelektrane. Kako u svetu dominira primena tehnoloških postupaka za odsumporavanje dimnih gasova zasnovanih na mokrim postupcima zbog visoke efikasnosti u otklanjanju SO2, ekonomske isplativosti i dobijanja gipsa kao nusproizvoda, može se očekivati da će se ovaj postupak primenjivati i u termoelektranama u Srbiji. Ovaj rad predstavlja pregled tehnoloških postupaka za odsumporavanje dimnih gasova, kao i pravne i ekonomske aspekte postupaka. Laboratorija za istraživanje upravljanja rizicima američke Agencije za zaštitu životne sredine objavila je model za izračunavanje troškova zaštite životne sredine kod upotrebe uglja. Ovaj model daje okvirnu procenu troškova koja može služiti kao polazna osnova za procenu troškova odsumporavanja dimnih gasova u termoelektranama u Srbiji.Combustion of coal results in sulfur dioxide (SO2) emissions which cause detrimental impacts on the environment and human health. Electric power generating units account for the majority of SO2 emissions in Serbia. Environmental regulations in Serbia require gradual implementation of flue gas treatment technologies for control the emissions of pollutants into the atmosphere. As far as Serbian thermal power plants are concerned, the basic design of systems for flue gas desulphurisation has been developed for two thermal power plants. As wet limestone-based FGD technologies dominate in the world because of high SO2 removal efficiency, cost effectiveness, and gypsum as the by-product, it is expected that Serbian thermal power plants will use this technology. This paper presents a review of commercially available FGD technologies, as well as legal and economic perspective of the process. U.S. EPA's National Risk Management Research Laboratory has published the Coal Utility Environmental Cost Workbook which provides the rough-order-of-magnitude budgetary cost estimates as the starting point for the limestone forced oxidation cost model that might be a good starting point for cost estimates for Serbian electric utilities
Preliminary Examination of the System Fly Ash-Bottom Ash-Flue Gas Desulphurization Gypsum-Portland Cement-Water for Road Construction
No full textThe paper describes an investigation into the use of three power plant wastes: fly ash, flue gas desulphurization gypsum, and bottom ash for subbase layers in road construction. Two kinds of mixtures of these wastes with Portland cement and water were made: first with fly ash consisting of coarser particles ( LT 1.651 mm) and second with fly ash consisting of smaller particles ( LT 0.42 mm). The mass ratio of fly ash-Portland cement-flue gas desulphurization gypsum-bottom ash was the same (3:1:1:5) in both mixtures. For both mixtures, the compressive strength, the mineralogical composition, and the leaching characteristics were determined at different times, 7 and 28 days, after preparation. The obtained results showed that both mixtures could find a potential use for subbase layers in road construction
Mechanical properties of forgings obtained from 7075 Al-alloy casted under electromegnetic field influence
No full textU radu su prikazani osnovi elektromagnetnog postupka livenja aluminijumske legure EN AW 7075 kao i rezultati mehaničke karakterizacije otkovka od ove legure koja je dobijena livenjem klasičnim polukontinualnim postupkom livenja i livenjem pod dejstvom elektromagnetnog polja sa dve različite frekvence. Rezultati pokazuju da uzorci otkovaka dobijeni od legure koja je livena u elektromagnetnom polju imaju zadovoljavajuće vrednosti mehaničkih svojstava i da se pravilnim izborom radnih parametara livenja mogu stvoriti uslovi za skraćenje tehnološkog postupka prerade ove legure.The electromagnetic casting process fundamentals of EN AW 7075 Al-alloy casting, as well as the mechanical characterization results of this alloy forgings are presented in this paper. Forgings are obtained from the alloy casted by classical semi-continuous casting process and by electromagnetic casting process using two different frequencies. Results reveal that forgings obtained from the alloy casted by electromagnetic casting process have adequate values of mechanical properties and that proper choice of operating parameters can lead to shortening of this alloy processing
Correlation between grade and recovery of copper concentrate from 'Veliki Krivelj' flotation plant in the function of grinding fineness
No full textCilj istraživanja čiji su rezultati prikazani u ovom radu bio je da se utvrdi zavisnost tehnoloških pokazatelja flotacijske koncentracije bakra od finoće mlevenja rude iz ležišta 'Veliki Krivelj', kao i da se ustanovi korelacija između iskorišćenja i sadržaja bakra u koncentratu. U toku ispitivanja procentualna masena učešća klase -0,074 mm iznosila su 58%, 60% i 65%. Na osnovu dobijenih rezultata utvrđeno je da se najveća iskorišćenja postižu pri finoći mlevenja od 65% -0,074 mm, dok je najbolji kvalitet koncentrata ostvaren pri finoći mlevenja od 60% -0,074mm. Međusobna zavisnost iskorišćenja i sadržaja bakra u koncentratu koji su dobijeni u ovim ispitivanjima može se prikazati polinomnom funkcijom trećeg stepena.The aim of the research whose results are presented in this paper was to determine the dependence of technological indicators of copper flotation on grinding fineness of ore from the deposit 'Veliki Krivelj', as well as to establish concentrate grade-recovery correlation. During this testing, the percentage mass share of class -0.074 mm was 58%, 60% and 65%, respectively. On the basis of the obtained results, it was found that the highest recovery of copper was achieved at grinding fineness of 65% -0.074 mm, and the best quality of concentrate at grinding fineness of 60% -0.074 mm. Interdependence of copper concentrate grade and recovery can be presented by polynomial function of the third degree, in this case
Dissolution behavior of a polyphosphate glass into an aqueous solution under static leaching conditions
No full textThe dissolution behavior of a polyphosphate glass with a molar ratio [M2O + MO]/P2O5>1 in distilled water under static condition was studied. The leaching tests were performed with glass powder samples (0.1-0.65 mm) at T=15-50 degrees C for times up to 720 h. The mass loss of the samples, the changes of pH and the concentration of elements (P, K, Ca, Mg, Zn and Mn) in solution were determined. The effects of temperature, time and particle size were analyzed. The results of the tests showed a complex dissolution behavior of this glass. The selective dissolution of the glass components was determined. The mechanism of formation and the structure of dissolved glass layer were investigated. The effects of cations on the mechanisms and kinetics of dissolution of the polyphosphate glass are presented. The activation energy of dissolution, Ea, was determined to be 39 +/- 5 kJ/mol
Removal of heavy metals from aqueous solution using natural and fe(iii) oxyhydroxide clinoptilolite
No full textThe increasing levels of industrial wastewater released to the environment present a serious threat to human health, living resources, and ecological systems. Fe-modified zeolites were developed and tested for removal of Cu2+ and Zn2+ from contaminated water. The surfaces of the naturally occurring zeolite, clinoptilolite, were modified with Fe(III) oxyhydroxides using three different methods, denoted I, II, and III (FeCli(1), FeCli(2), and FeNaCli(1), respectively). The oxyhydroxides were prepared in Method I using 0.1 M FeCl3 center dot 6H(2)O in an acetate buffer (pH = 3.6); in Method II, using 10% FeCl3 center dot 6H(2)O solution in 0.1 M KOH (pH = 10); and Method III was the same as Method I except the clinoptilolite was pretreated with NaCl. Newly synthesized materials from these three methods were then tested for their ability to enhance the sorption capacity for Cu and Zn compared to the natural sample (Cli). Powder X-ray diffraction measurements and the chemical composition of these modified samples confirmed that clinoptilolite maintained its structure while amorphous Fe3+ species were synthesized. The specific surface area (BET method) of both the natural and modified clinoptilolite increased by 2 and 7.5 times for Methods I and II, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed that CaO was formed during Method I (FeCli(1)). Throughout the adsorption process, the hydrolysis of CaO and the release of OH- caused the precipitation of Cu and Zn hydroxide, which made the determination of the sorption capacity of FeCli(1) impossible. This phenomenon was avoided in Method III (FeNaCli(1)) because of the absence of exchangeable Ca2+. The adsorption experiments with Method II resulted in double-enchanced adsoprtion capacity. Laboratory batch experiments revealed that the sorption capacities increased in the following order: Cli LT FeCli(2) LT FeNaCli(1), for Cu: 0.121 mmol/g LT 0.251 mmol/g LT 0.403 mmol/g and for Zn: 0.128 mmol/g LT 0.234 mmol/g LT 0.381 mmol/g
Chemical Thermodynamic Processes at Metal-Mold Interface
No full textAt the contact surface between the liquid metal and the mold wall a number of chemical and thermodynamical reactions were taken. The products of those reactions are spread out on both the sides, i.e., in the solidified metal or into the mold wall. The processes which took place in the casting mold-here made from sand mix, during the pouring of liquid metal, solidification and cooling down to room temperature, are pretty complex. The thermodynamic reactions at the contact surface of liquid metal/sand mold in the process of castings forming are discussed in this paper. Experiments were performed in molds made by CO2 sand casting process. As a pouring metal we used steels from an ordinary production program of a steel foundry, exactly it was the steel GS 50CrMo4, assigned by DIN. Some results obtained in our investigations during studying those processes are shown here
The influence of soil type on maize and wheat uranium uptake
No full textOne of the ways that uranium enters the environment is via the use of mineral phosphate fertilisers. A further route of uranium depends on soil properties, grown plants and groundwater. The uranium mobility in soil is regulated by environmental pH, red-ox potential, soil structure and mineral composition of a solid phase. The aim of this research was to define the levels and trends of uranium distribution in three different soil types and organs of grown maize and wheat, due to the long-term application of phosphate fertilisers. Uranium content was determined in plants and soil types. Fresh plants were washed, dried and burned. Final ash was further processed for determination of uranium concentration by fluorescent spectroscopy. The results indicated that the concentrations of uranium in fertilised soils were within its natural limits. Significant differences in uranium content in various parts of maize and wheat were found to be subject to the soil type, which was not the case regarding the nutrition treatment. In the three soil types tested, the results suggested that uranium concentration in soil decreases with an increase in soil acidity, which is in contrast to its accumulation in roots of cultivated plants
Characterization of lead sorption by the natural and Fe(III)-modified zeolite
No full textThe influence of contact time, temperature and particle size on lead sorption by the natural and Fe(III)-modified zeolites was investigated. Characterization of the natural and Fe(III)-modified zeolite before and after lead sorption was performed by determination of textural properties, by scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM-EDS), transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD) analysis. Lead sorption kinetics at 303-333 K, best represented by the pseudo-second order model and activation energy (13.5 and 8.5 kJ/mol for the natural and Fe(III)-modified zeolite respectively) confirmed an activated chemical sorption. Desorption experiments indicated that lead was irreversibly sorbed on both zeolites. XRPD, TEM and SEM results showed that modification of the natural zeolite with Fe(III) ions did not change its crystal structure and iron is mainly located at the zeolite surface, likely in form of amorphous iron oxy-hydroxides. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions (from 30.2 for the natural to 52.5 m(2)/g for Fe(III)-modified zeolite). Characterization of both lead saturated sorbents suggested that besides ion exchange, lead is both chemisorbed and precipitated at their surfaces, and presence of amorphous iron in Fe(III)-modified zeolite favors sorption of lead